Two Boston firefighters died and 18 other first responders were hospitalized after a nine-alarm fire tore through a brownstone building in Boston's fashionable Back Bay neighborhood Wednesday, trapping firefighters in the basement, officials said.

"People were saved by the actions they did in the fire today," said Rich Paris, president of the Boston firefighters union, at a Wednesday evening news conference. "That’s what we do. We sacrifice our lives for the citizens of Boston."

No civilian casualties were reported in the fire, which began in the basement of a four-story Beacon Street brownstone before spreading upward and growing into a nine-alarm blaze, the Boston Fire Department said on its official Twitter account.

That account tweeted several dramatic photos of firefighters battling the blaze before going into a long silence.

"There are reasons why we stopped posting to Twitter. Will be explained later," read a following tweet.

Lt. Edward J. Walsh of West Roxbury, a father of two boys and a girl, all younger than 10, and firefighter Michael Kennedy, a U.S. Marine veteran, were killed in the fire. They would have been among the first firefighters to respond to the blaze, officials said.

Both men were apparently trapped in the basement as the fire raged, at one point making an explosion-like backdraft, officials said. The fire "was blowing like a blowtorch from the front," Boston Deputy Fire Chief Joseph Finn told reporters.

Emergency radio traffic painted fragments of a dramatic scene at the building, with one emergency official telling responders, "All companies out of the building, now!"

A male responder radioed, "I’m at zero. Getting hot down here!" with another adding, "I'm running out of water, I'm running out of water."

A female voice, apparently a dispatcher, told another official, "They say they don’t have any water; it’s getting hot in there. … They’re in the basement heading toward the front of the building."

Sam Wallace, president of the Neighborhood Assn. of the Back Bay, told the Boston Globe that he saw people "running out of the building screaming" as well as several soot-faced firefighters being placed into ambulances.

Officials said 13 of the 18 people hospitalized from the fire were firefighters, and Nick Martin, spokesman for the Boston Public Health Commission, told the Los Angeles Times that the other five were first responders.

Fire officials said they weren’t aware whether any of the injuries were serious.